1. Field of the Invention
The invention relates generally to blood pressure measuring devices and particularly to a new cuff design for a blood pressure measuring device.
2. Background of the Prior Art
According to the auscultatory method of measuring blood pressure, a health care provider wraps a pneumatic cuff, including an inflatable section and an end section, around an arm of a patient such that the inflatable section of the cuff lies directly over the brachial artery, and then occludes the artery by inflating the inflatable section to a pressure exceeding the systolic pressure of the artery. The health care provider then slowly decreases pressure in the bladder, and with use of a stethoscope, listens for changes in the sound made by blood flowing through the artery.
At the point where the bladder pressure equals the systolic pressure of the artery, blood begins to flow through the artery. The pressure reading of the bladder at the time blood flow becomes audible is the systolic pressure of the artery.
For accurate blood pressure reading, the inflatable section of the cuff must occlude a substantial length of the brachial artery. Most studies conclude that an inflatable section width of about 40 percent of the circumference of an arm will ensure adequate occlusion of the artery. If the bladder occludes only a short length of artery then the pressure reading of the bladder at the time the blood begins to flow through the artery will be greater than the actual systolic pressure of the artery, resulting in an erroneously high systolic blood pressure reading.
A conventional cuff design of the prior art includes a rectangular shaped end portion which is adapted to be wrapped uniformly about substantially cylindrical objects. Because the majority of patients have biceps of substantially uniform circumference, the conventional cuff design of the prior art applies even pressure along a substantial length of the brachial artery during blood pressure reading and is therefore effective in providing accurate blood pressure readings in most cases.
Unfortunately, some patients, particularly overweight patients, do not have arms of substantially uniform circumference. When a blood pressure cuff of a conventional design is applied to patients having nonuniform-circumferenced, or "tapered" arms, the bladder portion of the cuff tends to apply significant pressure only to a short length of the brachial artery, and leads to erroneous blood pressure readings.
Pressure cuffs having essentially the same design as blood pressure cuffs are used for a variety of medical procedures including plethysmography.
There exists a need for a pressure cuff which can accurately and reliably apply substantial even cuff pressure to the arms of patients having arms of substantially nonuniform circumference.